The present invention relates to a method for making a semiconductor substrate having a strained silicon layer for improved device performance. More particularly the method utilizes a porous silicon layer and a relaxed silicon germanium (SiGe) layer to achieve a strained Si layer for improved device performance (mobility). One application of this strained layer is to improve the channel mobility for FETs in CMOS applications on Silicon-On-Insulator (SOI) substrates (also referred to as wafers).